Phenytoin is 5,5-diphenyl-2,4-imidazolidinedione. It is a well-known pharmaceutical agent having anticonvulsant and antiepileptic activity. Its preparation is described in U.S. Pat. No. 2,409,754.
Due to phenytoin's poor solubility in water, phenytoin sodium, of empirical formula C.sub.15 H.sub.11 N.sub.2 NaO.sub.2, which is more soluble, is employed in the preparation of injectable solutions of the drug. In order to stabilize solutions of phenytoin sodium, it is conventional to employ aqueous alcoholic solvent systems. One conventional component of such systems, propylene glycol, has been associated with undesirable side effects.
The need arose for stable aqueous preparations based on phenytoin which did not contain potentially dangerous solvents, e.g., propylene glycol.